CCFL has been widely used for the backlight of display, especially the liquid crystal display (LCD), due to its advantages of power saving, low power dissipation, decreased heat generation, long life time, small size, light weight, high illumination, high color rendering, and moderate lamp temperature after long-term used. Conventionally, it is sufficient of only one CCFL for a display, because of the small size of the display. As the progress in technology, however, the display becomes larger and therefore the amount of the CCFLs served as the light source has to be increased. Thus, there is a need for a driving circuit capable of driving several CCFLs.
A driving circuit proposed by U.S. Pat. No. 6,396,722 issued to Lin comprises four MOS transistors and one transformer to be constituted a full-bridge circuit to drive CCFL. However, only one CCFL could be driven by this circuit, and several such individual full-bridge circuits are needed if several CCFLs to be driven. Further, due to the fact that MOS transistor and transformer are all costly elements, the more ones being used, the cost is higher.
Therefore, it is desired a driving circuit capable of driving several CCFLs with a reduced cost.